Systems for providing various types of information to terminals have been proposed conventionally. For example, teletext broadcasts, in which text code, graphical information, program-related information, and so forth are superimposed on (multiplexed with) the broadcast signal to provide various types of information in addition to regular programming content to the television receiver or radio receiver, have been carried out in the context of radio and television broadcasts.
However, because teletext broadcast systems require that digital information be superimposed on the television or radio signal on which it will ride, this has necessitated complex broadcast facilities, which has increased cost and made easy provision of information to terminals impossible. On the other hand, with respect to methods whereby cameras of mobile telephone are used to capture QR codes, not only are these incapable of being employed in situations where the terminal is not equipped with a camera, but the procedures involved are only carried out with great difficulty by beginners or those not already mechanically inclined.
In light of such problems, novel information-providing methods for providing various types of information to terminals as acoustic waves with air serving as medium have been developed. In one such method in which information is conveyed in the form of an acoustic wave, use of an existing speaker and a microphone installed at a terminal makes it possible to convey information easily and inexpensively.
In one such information-conveying system, an information-encoding apparatus that converts an information payload into audio is employed to convey the information payload as audio by way of the I/O interface of existing audio-handling acoustic equipment, the information payload being reproduced based on audio received by an information-decoding apparatus. In such a system, it may be an object of the encoding technique employed that sound containing encoded information is to be rendered as pleasant music which is deliberately intended to be heard by humans.
Furthermore, information-providing systems developed by the present inventors include information-providing systems that provide information in the form of acoustic waves, with various types of information being encoded as millisecond-order data frames that include preambles for synchronization of timing.
Furthermore, information-providing systems developed by the present inventors also include information-providing systems in which various types of information are transmitted as information in the form of sound pressure oscillations, at which time the frequencies of transmission thereof are made to lie in the gaps between respective notes in a tempered scale.
Here, during use of such systems for conveying information as acoustic waves, because the acoustic waves which convey the information are audible sounds, there are cases where, depending on ambient conditions, these may be unpleasantly perceived as annoying by the human ear. Where this is the case, there is a possibility that transmission of acoustic waves for the purpose of conveying information at a store would cause customers who react unpleasantly to this to leave the store.
The present invention was conceived in light of such problems, it being an object thereof, in environments permitting information to be conveyed as acoustic waves, to provide a transmitter that is capable of causing acoustic waves that convey information to be not easily perceived by the human ear.